Nate, the hookah he has is not an AF, he just pointed out that the only other hookah available to him are the AF hookahs he linked to.
The hookahs you linked to do appear to be real AF hookahs, at least the first one for sure and I would guess the others as well.
As for replacing the rusted stem, yes you probably could get a replacement but being as it was a cheap hookah to begin with, your best bet is to just get a new hookah. A replacement stem would likely cost about the same as you paid in the first place. Either get another cheap hookah to hold you over or just start saving up for a good one.